Manufacture of fused chemical pellets



Jan. 6, 1942.

F. c; MERICOLA 2,268,888

MANUFACTURE OF FUSED CHEMICAL PELLETS Filed March 28, 1939 INVENTOR. w" I G- EL BY FRANCIS c. uemcoLA 1 HG- '7 Y. t 9

A'ITORN 5.

Patented Jan. 6, 1942 MANUFACTURE or rosancnnmcsr.

-- rmu'rs Francis C. Mericola, Wyandotte, Mich, asslgnor to Michigan Alkali Company,

Wyandotte,

Micln, a corporation of Michigan Application March 28 1939, Serial No. 264,577

7 Claims.

The present invention relates to a method and apparatus for forming or fabricating fused, i. e., molten chemical materials, such as caustic soda, calcium chloride and the like into solidified droplets or pellets. I

Heretofore it has been known that such chemical materials could be produced in pellet form generally bythe process of forming the molten, fluid material into drops and solidifying such drops upon a cold or cooling surface. My present invention constitutes an improvement in this previously known procedure and has for its general object the production of particles ,of uniform size and shape with a regular contour, viz., with v the absence of tails or teats on thedroplets or pellets. The process of manufacture embodied in my invention provides for accurate and. reliable control in the shape of the pellets, in the rate of formation thereof, and also in the temperature of the fused or molten material which is to be formed into drops, before being deposited upon the cooling surface. The control of the temperature of the material incidentally involves such factors as surface tension and viscosity, which in turn have a bearing upon the drop forming and shaping step of the process. My invention possesses the further advantage in that it eliminates the necessity for separate and additional apparatus for heating the material in the dropping box, and at the same time insures the maintenance of uniform temperature, surface tension and viscosity throughout the body of the material present in the dropping boxes.

To the accomplishment of the foregoing and related ends, said invention, then, consists of the means hereinafter fully described and particularly pointed out in the claims, the annexed drawing and the following description setting forth in detail certain means and one mode of carrying out the invention, such disclosed means and mode illustrating, however, but one of various ways in which the principle of the invention may be used.

In said annexed drawing:

Fig. 1 is an elevational, assembly view illustrating apparatus embodying my invention and adapted to perform the process thereof; Fig. 2 is a right hand end view of Fig. 1; Fig. 3 is a vertical sectional view taken through one of the dropping tubes; Fig. 4 is a sectional viewtaken through the droppingbox; and Figs. 5 to 8 inclusive are perspective views illustrating the various forms of pellets capable of being produced by my method and apparatus.

Now referring more particularly to the drawing, the apparatus shown therein includes a melting pot for the reception of a chemical material such as caustic soda, calcium chloride or the like, and for heating such material to a fused orliquid "molten condition; A conduit 2 leads from near the'bottom of the melting pot i to the hydraulic pump 3 which is in turn driven by the variable speed electric motorl. The motor I is shown connected to the adjustable rheostat 5 whereby itsspeed and of course the rate of delivery of the pump 3 can be adjustably regulated. The flexible outlet conduit 6 leads fromthe discharge side of the pump 3 to the inlet pipe 1 into the interior of the dropping box 8. The outlet pipe 8 leads from the end of the dropping box I opposite to that of the inlet pipe I, and through the flexible conduit l0 back to the melting pot I.

A series of dropping tubes II are mounted in the botom wall ill of the dropping box 8. The? upper ends of the dropping tubes H are cut oil at an angle of about 45 to the horizontal, thus presenting an inlet opening or orifice H for the interior of the tubes whose marginal edges are disposed in a plane intersecting or non-parallel to the liquid level of .the material A in the dropping box 8. Thus, the open end or orifice iii of the dropping tubes Ii functions as a weir or darn over which the material must pour or spill in a sheet-like form, as indicated at B. As the material reaches the lower end of the tube I I, it builds up into a solid body filling the interior of the tube as indicated at C. As soon as the weight of the body of material C overcomes the capillary attraction to the walls of the tube. it then forms into a cylindrical drop which drops out of the lower end of the tube.

The lower ends of the tubes II are cone shaped or beveled on the outside as indicated at II. The presence of this cone shaped tip It prevents the fluid material from creeping" sideways along a horizontal surface to form'drops of non-uniform pipe 28. A hopper or receiver 24 is located adto the horizontal shaft 88. The latter is operated or rotated by means of a hand wheel 8|. In this manner the pouring box 8 and the dropping tubes II can be moved to any desired position with respect to the cooling surface or endless belt aaeaeaa dropping tubes II from making up" or the material therein from freezing out. If the rate of circulation of the material through the dropping box 8 is increased to such a point that the liquid level of the material A rises above and completely covers the orifice II, a solid stream of material will be deposited upon the endless belt l8, resulting in the formation of a ribbon oi solidified material which uopn discharge over l5, and serves as means for conveniently effecting the control of the contour or shape of the solidified pellets. Thus, a semi-spherical pellet, such as illustrated in Fig. 5, will be formed when the dropping box 8 is in a relatively low position with respect to the belt IS. A disc-like or discoid form of pellet, as shown in Fig. '7, will be formed when the dropping box is in a relatively high position with respect to the belt l5. Fig. 6 illustrates an intermediate semi-ellipsoidal shape pellet, corresponding to an intermediate height location of the dropping box 8.

The operation of the above described apparatus should now be fairly apparent. The molten, fused material is pumped from the melting pot l to the dropping box 8 where it rises to a predetermined liquid level dependent upon the delivery speed of the pump 8 and the rate of flow return through the return conduit I 0. The molten, fused material is thus circulated through the dropping box 8 and a portion of it enters the openings or orifices I! in the top of the dropping tubes ll, whence it is formed into drops as previously described and deposited upon the cooling surface of the endless belt IS. The drops then become solidified into droplets or pellets which are discharged by gravity from the end of the belt l5 into the hopper 24. By increasing the speed of the pump 3, the liquid level of the body A of molten material in the dropping box 8 may be raised to increase the rate of formation of the drops, as well as to serve as a very accurate means of controlling the temperature, within limits of the material in the box. This temperature control arises from the fact that there is bound to be a heat loss, and therefore a temperature drop in the material as it is removed from the melting pot i to the dropping box 8. The-greater the rate of flow of material through the dropping box 8, the lower the proportionate amount of heat loss and temperature drop. Thus, at a relatively low rate of circulation of the material through the box 8, the temperature of the material A therein will be relatively low, and by the same token a relatively higher tem-- perature will result with a relatively greater rate of flow.

The surface tension and viscosity of the material in the box 8 and of course that passing into the dropping tubes II, is a function of the temperature. Since the size of the drops, as represented by the body of material C, is in turn a function of surface tension and viscosity, it will thus be seen that the sizes of the drops formed can in turn be controlled by the pumping rate or rate of circulation of the material through the box 8. 1

Furthermore the circulation of the excess material through the dropping box 8 prevents the the right hand end of the belt II will be broken up into smaller pieces such as indicated in Fig. 8.

It will thus be seen that the above described method and apparatus is capable of producing fused. andsubsequently solidified chemical materials in pellet form with a convenient, flexible and relatively simple control over the size, shape and contour of the pellets. Due to the fact that the drops which are formed by the tubes II, drop off cleanly from the lower ends thereof, not only is the previously indicated objection of "creeping and formation of non-uniform sized drops eliminated, but also the tendency to form "tails or teats" on the pellets is substantially decreased.

Other modes of applying the principle of my invention may be employed instead of the one explained, change being made as regards the means and the steps herein disclosed, provided those stated by any of the following claims or their equivalent be employed.

I therefore particularly point out and distinctly claim as my invention:

1. A method of forming fused chemical material into pellets comprising the steps of circulating the molten material into, through, and out of, a drop forming chamber, withdrawing a lesser portion of such material than that circulated in the form of droplets from said chamber and dropping them on a cooling surface to form soiidifled pellets, and controlling the temperature and fluidity of that portion of material instantaneously in said chamber by varying the rate of such circulation. 2. Apparatus for forming a fused chemical material into pellets comprising a chamber for the reception of a body of said material, and a plurality of tubes extending through the bottom of said chamber, the lower ends of said tubes being externally cone shaped, and the upper ends thereof being disposed at an angle to the horizontal.

3. Apparatus for forming a fused chemical material into pellets comprising a chamber for the reception of a body of said material, a plurality of tubes extending through the bottom of said chamber, the upper ends of said tubes extending above said bottom and into the interior of said chamber, said upper ends being disposed at a horizontally inclined angle whereby the opening to the interior of said tubes is disposed in a plane intersecting and non-parallel to the liquid level of said material and said chamber.

4. Apparatus for forming a fused chemical material into pellets comprising a chamber for the reception of a body of said material, a plurality of tubes extending through the bottom of said chamber, the lower ends of said tubes being externally cone shaped, the upper ends of said tubes extending above said bottom and into the interior of said chamber, said upper ends being disposed at a horizontally inclined angle whereby the opening to the interior of said tubes is disposed in a plane intersecting and non-parallel to the liquid level of said material and said chamber.

5. Apparatus for forming a fused chemical material into pellets comprising a melting pot for said material, a separate drop forming chamber, means for circulating said material from said melting pot into and through said chamber and thence to return to said melting pot, a cooling surface located below said chamber, and a pluralit-y of tubes extending through the bottom of said chamber having their upper ends disposed at an angle to the horizontal.

6. Apparatus for forming a fused chemical material into pellets comprising a melting pot for said material, a separate drop forming chamber, means for circulating said material from said melting pot into and through said chamber and thence to return to said melting pot, a cooling surface located below said chamber, a pump for withdrawing material from said melting pot, a conduit leading from said pump to said chamber, a return conduit from said chamber to said melting pot, a cooling surface located below said chamber, and a plurality of tubes extending though the bottom of said chamber having their upper ends disposed at an angle to the horizontal.

7. Apparatus for forming a fused chemical material into pellets comprising a melting pot for said material, a separate chamber, a plurality of tubes extending through the bottom of said chamber, the lower ends of said tubes being externally cone shaped, the upper ends of said tubes extending above said bottom and into the interior of said chamber, said upper ends being disposed at a horizontally inclined angle whereby the opening to the interior of said tubes is disposed in a plane intersecting and non-parallel to the liquid level of said material in said chamber, a pump for withdrawing material from said melting pot, a conduit leading from said pump to one end of said chamber, a return conduit leading from the opposite end of said chamber to said melting pot, an endless belt having one end located underneath said lower ends of said tubes, and means for moving and cooling said endless belt.

FRANCIS C. MERICOLA. 

